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/*
* Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package gc.g1.unloading.bytecode;
import java.io.*;
import java.nio.charset.*;
import java.util.*;
/**
* This BytecodeFactory produces bytecode that is golden bytecode with className substituted.
*/
public class BytecodeMutatorFactory implements BytecodeFactory {
private static final String FILLER_CHARACTER = "_";
/**
* Utility method in this class
*/
public static String padName(String s, int length) {
int difference = length - s.length();
StringBuilder sb = new StringBuilder(s);
for (int i = 0; i < difference; i++) {
sb.append(FILLER_CHARACTER);
}
return sb.toString();
}
public String padName(String s) {
return padName(s, getNameLength());
}
private final Charset CHARACTER_SET = StandardCharsets.UTF_8;
private List<Integer> offsets = new LinkedList<>();
private byte[] templateBytecode;
private String templateClassName;
private byte[] templateClassNameAsBytes;
public BytecodeMutatorFactory() {
this(DefaultTemplateClass.class.getName());
}
public BytecodeMutatorFactory(String templateClassName) {
this.templateClassName = templateClassName;
// Read bytecode to array
InputStream is = ClassLoader.getSystemResourceAsStream(templateClassName.replace('.', '/').concat(".class"));
try {
templateBytecode = new byte[is.available()];
is.read(templateBytecode);
is.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
// Save offsets
templateClassNameAsBytes = templateClassName.replace('.', '/').getBytes(CHARACTER_SET);
for (int i = 0; i < templateBytecode.length; i++) {
boolean match = true;
for (int j = 0; j < templateClassNameAsBytes.length; j++) {
if (i + j >= templateBytecode.length || templateClassNameAsBytes[j] != templateBytecode[i + j]) {
match = false;
break;
}
}
if (match) {
offsets.add(i);
}
}
}
public byte[] getBytecode(String className) {
// Check size of name constraint
byte[] newClassNameAsBytes = className.replace('.', '/').getBytes(CHARACTER_SET);
if (newClassNameAsBytes.length != templateClassNameAsBytes.length) {
throw new RuntimeException("Can't produce bytecode with \"" + className + "\" substituted as class name. " +
"Length of this name differs from length of \"" + templateClassName + "\" which equals to " + templateClassName.length() +
". Length of \"" + className + "\" is " + className.length() + ".");
}
// Prepare bytecode
byte[] result = Arrays.copyOf(templateBytecode, templateBytecode.length);
for (int offset : offsets) {
System.arraycopy(newClassNameAsBytes, 0, result, offset, newClassNameAsBytes.length);
}
return result;
}
public int getNameLength() {
return templateClassName.length();
}
@Override
public Bytecode createBytecode(String className) {
String finalClassName = padName(className);
byte[] bytecode = getBytecode(finalClassName);
return new Bytecode(finalClassName, bytecode);
}
}
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